Systems and methods for diagnosing auxiliary equipment associated with an engine

ABSTRACT

Diagnosing auxiliary equipment associated with an engine. A condition of the auxiliary equipment is diagnosed based on information provided by signals from a generator operationally connected to the auxiliary equipment or other signals associated with the engine. Different types of degradation are distinguished based on discerning characteristics within the information. Thus, a degraded auxiliary equipment component can be identified in a manner that reduces service induced delay.

This application claims the benefit of U.S. provisional patentapplication Ser. No. 61/535,049, filed on Sep. 15, 2011, which is herebyincorporated by reference in its entirety.

FIELD

Embodiments of the subject matter disclosed herein relate to systems anda methods for diagnosing an engine and associated auxiliary equipment.

BACKGROUND

Engine components and associated auxiliary equipment components maydegrade during operation in various ways. For example, an enginecylinder in an engine may start mis-firing due to a worn out ignitionplug. A radiator fan (auxiliary equipment) may start wobbling due to anunbalanced fan blade. The performance of a traction motor (auxiliaryequipment) may degrade due to an open circuit in a motor coil winding.

One approach to detect engine degradation or auxiliary equipmentdegradation is to monitor engine speed. Diagnostic routines can monitorwhether components of the engine speed rise above a threshold level, andgenerate diagnostic codes or other indications requesting service,de-rating engine power, shutting down the engine, derating auxiliaryequipment power, or shutting down the auxiliary equipment.

However, the inventors herein have recognized that analysis of enginespeed is often inadequate to thoroughly diagnose an engine problem or anauxiliary equipment problem. Furthermore, engine speed is oftendisassociated with certain types of auxiliary equipment (e.g., auxiliaryequipment running off of a generator (alternator) connected to theengine such as a radiator fan or a traction motor.

BRIEF DESCRIPTION

In one embodiment, a method for auxiliary equipment electrically coupledto a generator that is operationally connected to a reciprocating engineis disclosed. The method includes measuring a dc-link parameterassociated with the generator during operation, and diagnosing acondition of the auxiliary equipment based on frequency content of thedc-link parameter.

In one embodiment, a method for auxiliary equipment operationallyconnected to a rotating shaft of a reciprocating engine is disclosed.The method includes measuring a rotating shaft speed of thereciprocating engine during operation, and diagnosing a condition of theauxiliary equipment based on a frequency content of the shaft speed.

In one embodiment, a vehicle system is disclosed. The vehicle systemincludes a generator, auxiliary equipment electrically coupled to thegenerator, a dc-link sensor for measuring a dc-link parameter associatedwith the generator during operation, and a controller. The controllerincludes instructions configured to sample and transform the measureddc-link parameter, identify frequency content of the dc-link parameter,and diagnose a condition of the auxiliary equipment based on thefrequency content of the dc-link parameter.

In one embodiment, a vehicle system is disclosed. The vehicle systemincludes a reciprocating engine having a rotating shaft, auxiliaryequipment operatively coupled to the rotating shaft, a sensor formeasuring a speed of the rotating shaft over time during operation, anda controller. The controller includes instructions configured to sampleand transform the measured speed, identify frequency content of thespeed, and diagnose a condition of the auxiliary equipment based on thefrequency content of the speed.

In one embodiment, a test kit is disclosed. The test kit includes acontroller that is operable to determine a condition of an auxiliaryequipment electrically coupled to a generator based on frequency contentof a measured dc-link parameter associated with the generator over time.

In one embodiment, a test kit is disclosed. The test kit includes acontroller that is operable to determine a condition of an auxiliaryequipment operatively coupled to a rotating shaft of a reciprocatingengine based on frequency content of a measured speed of the shaft overtime.

This brief description is provided to introduce a selection of conceptsin a simplified form that are further described herein. This briefdescription is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter. Furthermore, the claimedsubject matter is not limited to implementations that solve any or alldisadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood from reading the following descriptionof non-limiting embodiments, with reference to the attached drawings,wherein below:

FIG. 1 is an illustration of an example embodiment of a vehicle system(e.g., a locomotive system), having an engine and a generator(alternator), herein depicted as a rail vehicle configured to run on arail via a plurality of wheels;

FIG. 2 is an illustration of an example embodiment of the engine andgenerator of FIG. 1 operatively connected to various auxiliary equipment140 and traction motors;

FIG. 3 is an illustration of example embodiments of how to generatefrequency content from a time sampled dc-link parameter;

FIG. 4 is an illustration showing example embodiments of “healthy” and“unhealthy” frequency content;

FIG. 5 is an illustration of an example embodiment of how a diagnosticlogic in the controller can detect an unhealthy condition in thefrequency content of a dc-link parameter;

FIG. 6 is an illustration of an example embodiment of how to isolate adegradation to a particular auxiliary system; and

FIG. 7 is an illustration of an example embodiment of how to diagnose acondition of auxiliary equipment using a bank of tuned bandpass filters.

DETAILED DESCRIPTION

Embodiments of the subject matter disclosed herein relate to systems anda methods for diagnosing auxiliary equipment associated with an engine.Test kits for performing the methods are provided, also. The engine maybe included in a vehicle, such as a locomotive system. Other suitabletypes of vehicles may include on-highway vehicles, off-highway vehicles,mining equipment, aircraft, and marine vessels. Other embodiments of theinvention may be used for stationary engines such as wind turbines orpower generators. The engine may be a diesel engine, or may combustanother fuel or combination of fuels. Such alternative fuels may includegasoline, kerosene, biodiesel, natural gas, and ethanol—as well ascombinations of the foregoing. Suitable engines may use compressionignition and/or spark ignition. These vehicles may include an enginewith components that degrade with use.

Furthermore, embodiments of the subject matter disclosed herein usegenerator data, such as measured generator electrical parameters orgenerator data (e.g., a derived torque profile) derived from measuredgenerator electrical parameters and/or engine parameters (e.g., speed),to diagnose conditions of auxiliary equipment and to distinguish betweenconditions and associated engine components and auxiliary equipment.

An engine may be put in a particular operating condition, state, or modewhen looking for particular types of engine degradation. For example,the engine may be diagnosed during a self-loaded condition as part of atest procedure, a dynamic brake (db) setup condition, or a steady statemotoring condition. Similarly, an auxiliary system may be put in aparticular operating condition, state, or mode when looking forparticular types of auxiliary equipment degradation. The diagnostic andprognostic methods discussed herein can be used for trending, comparingcylinder-to-cylinder variation, performing test procedures, repairconfirmation, and aid in repair. Alternatively, generator and/or enginedata may be sampled and analyzed when the engine reaches a particularoperating condition or state during normal operation.

FIG. 1 is an illustration of an example embodiment of a vehicle system100 (e.g., a locomotive system) herein depicted as a rail vehicle 106configured to run on a rail 102 via a plurality of wheels 108. Asdepicted, the rail vehicle 106 includes an engine 110 operativelyconnected to a generator (alternator) 120. The vehicle 106 also includestraction motors 130 operatively connected to the generator 120 fordriving the wheels 108. The vehicle 106 further includes variousauxiliary systems or equipment 140 operatively connected to thegenerator 120 or the engine 110 (e.g., the rotatable engine shaft 111,see FIG. 2) for performing various functions. Even though labeledseparately in FIG. 1, the traction motors 130 are considered to be atype of auxiliary equipment herein.

The vehicle 106 further includes a controller 150 to control variouscomponents related to the vehicle system 100. In one example, controller150 includes a computer control system. In one embodiment, the computercontrol system is largely software based and includes a processor, suchas processor 152, configured to execute computer operable instructions.The controller 150 may include multiple engine control units (ECU) andthe control system may be distributed among each of the ECUs. Thecontroller 150 further includes computer readable storage media, such asmemory 154, including instructions (e.g., computer executableinstructions) for enabling on-board monitoring and control of railvehicle operation. Memory 154 may include volatile and non-volatilememory storage. In accordance with another embodiment, the controllermay be hardware based using, for example, digital signal processors(DSPs) or other hardware logic circuitry to perform the variousfunctions described herein.

The controller may oversee control and management of the vehicle system100. The controller may receive a signal from a speed sensor 160 of theengine or from various generator sensors 170 to determine operatingparameters and operating conditions, and correspondingly adjust variousengine actuators 162 to control operation of the rail vehicle 106. Inaccordance with an embodiment, the speed sensor includes a multi-toothpick-up wheel connected to the engine shaft 111, and a reluctance sensorfor sensing when a tooth of the pick-up wheel passes by the reluctancesensor. For example, the controller may receive signals representingvarious generator parameters from various generator sensors. Thegenerator parameters can include a dc-link voltage, a dc-link current, agenerator field voltage, a generator field current, a generator outputvoltage, and a generator output current. Other generator parameters maybe possible as well, in accordance with various embodiments.Correspondingly, the controller may control the vehicle system bysending commands to various components such as traction motors,alternator, cylinder valves, throttle, etc. Signals from generatorsensors 170 may be bundled together into one or more wiring harnesses toreduce space in vehicle system 100 devoted to wiring and to protect thesignal wires from abrasion and vibration.

The controller may include onboard electronic diagnostics for recordingoperational characteristics of the engine. Operational characteristicsmay include measurements from sensors 160 and 170, for example. In oneembodiment, the operational characteristics may be stored in a databasein memory 154. In one embodiment, current operational characteristicsmay be compared to past operational characteristics to determine trendsof engine and/or auxiliary equipment performance.

The controller may include onboard electronic diagnostics foridentifying and recording potential degradation and failures ofcomponents of vehicle system 100. For example, when a potentiallydegraded component is identified, a diagnostic code may be stored inmemory 154. In one embodiment, a unique diagnostic code may correspondto each type of degradation that may be identified by the controller.For example, a first diagnostic code may indicate a problem withcylinder 1 of the engine, a second diagnostic code may indicate aproblem with cylinder 2 of the engine, a third diagnostic code mayindicate a problem with one of the auxiliary systems, etc.

The controller may be further linked to display 180, such as adiagnostic interface display, providing a user interface to thelocomotive operating crew and a maintenance crew. The controller maycontrol the engine, in response to operator input via user inputcontrols 182, by sending a command to correspondingly adjust variousengine actuators 162. Non-limiting examples of user input controls 182may include a throttle control, a braking control, a keyboard, and apower switch. Further, operational characteristics of the engine andauxiliary equipment, such as diagnostic codes corresponding to degradedcomponents, may be reported via display 180 to the operator and/or themaintenance crew.

The vehicle system may include a communications system 190 linked to thecontroller. In one embodiment, communications system 190 may include aradio and an antenna for transmitting and receiving voice and datamessages. For example, data communications may be between vehicle systemand a control center of a railroad, another locomotive, a satellite,and/or a wayside device, such as a railroad switch. For example, thecontroller may estimate geographic coordinates of vehicle system usingsignals from a GPS receiver. As another example, the controller maytransmit operational characteristics of the engine and/or auxiliaryequipment to the control center via a message transmitted fromcommunications system 190. In one embodiment, a message may betransmitted to the command center by communications system 190 when adegraded component of the engine or auxiliary equipment is detected andthe vehicle system may be scheduled for maintenance.

FIG. 2 is an illustration of an example embodiment of the engine 110 andgenerator 120 of FIG. 1 operatively connected to various auxiliaryequipment 140 (141, 142, 143, 144) and traction motors 130. Variousmechanical auxiliary equipment 144 may be operatively coupled to anddriven by the rotating engine shaft 111. Other auxiliary equipment 140are driven by the generator 120 through a rectifier 210 that produces adc-link voltage to power regulators 230. Examples of such auxiliaryequipment include a blower 141, a compressor 142, and a radiator fan143. The traction motors 130 are driven by the generator 120 through therectifier 210 that produces a dc-link voltage to an inverter 220. Suchauxiliary equipment 140, traction motors 130, and their implementationsare well known in the art. In accordance with certain embodiments, thegenerator 120 may actually be one or more generators such as, forexample, a main generator to drive the traction motors 130 and anauxiliary generator to drive a portion of the auxiliary equipment 140.Further examples of auxiliary equipment include turbochargers, pumps,engine cooling systems, braking grids, and energy storage systems.

The speed sensor 160 measures the speed of the rotating shaft 111 of theengine during operation. The dc-link sensor 171 is a generator sensorand can measure dc-link voltage, dc-link current, or both, in accordancewith various embodiments. The field sensor 172 is a generator sensor andcan measure field current of the generator, field voltage of thegenerator, or both, in accordance with various embodiments. Inaccordance with certain embodiments, generator sensors 173 and 174 areprovided for measuring the armature output voltage and current of thegenerator, respectively. Suitable commercially available sensors may beselected based on application specific parameters.

Referring again to FIG. 2, the AC output of the generator 120 isrectified by the diode rectifier 210 to form a dc-link voltage that issupplied to various auxiliary systems or equipment over a dc bus. Thedc-link voltage drives some auxiliary equipment (e.g., blower 141,compressor 142, and radiator fan 143) through power regulators 230. Thedc-link voltage drives the traction motors 130 through an inverter 220.

In accordance with an embodiment, the dc-link voltage is measured by thedc-link sensor 171 and is analyzed by the controller 150 to diagnose acondition of the auxiliary equipment based on frequency content of thedc-link voltage. A Fourier transform process 310 or a bandpass filteringprocess 320 can be used to determine the frequency content of thedc-link voltage as shown in FIG. 3. For auxiliary systems that operateintermittently, time-frequency analysis techniques such as short timeFourier transformation or wavelet transformation may be used. As analternative, the dc-link current can be measured and used instead of thedc-link voltage. The controller 150 is configured to analyze one or morecomponents of the frequency content, isolate to a particular auxiliarysystem, and diagnose the condition of the particular auxiliary system(e.g., down to a particular component of the auxiliary system). Inaccordance with an embodiment, the engine 110 may first be driven to aspecified operating condition, state, or mode before diagnosing theauxiliary equipment.

The controller 150 samples the dc-link parameter over time and performsa frequency analysis process on the dc-link parameter data. Inaccordance with one embodiment, the frequency analysis process is aFourier transform process 310 (e.g., a Fast Fourier Transform, FFT,process). In accordance with another embodiment, the frequency analysisprocess is a bandpass filtering process 320. The frequency analysisprocess transforms the sampled time domain dc-link parameter intofrequency content in the frequency domain. The various frequencycomponents of the frequency content can include dc (zero order),fundamental (first order) and harmonic (second order, half order, thirdorder, etc.) frequency components. The fundamental frequencies for eachof the connected auxiliary systems could be different, depending on thespeed/mode of operation of the auxiliary systems. In accordance with anembodiment, the Fourier Transform process and the bandpass filteringprocess include computer executable instructions that are executed bythe processor 152. The frequency transformation can be performed onprocessed/derived signals such as, for example, kilovolt-amps (kVA) orkilowatts (kW) which are the product of current and voltage, or torquewhich is kW/frequency of the signal.

The engine may have a plurality of cylinders that fire in a predefinedsequence, where each cylinder fires once during a four stroke or a twostroke cycle. For example, a four cylinder, four stroke engine may havea firing sequence of 1-3-4-2, where each cylinder fires once for everytwo revolutions of the engine. Thus, the firing frequency of a givencylinder is one half the frequency of revolution of the engine and thefiring frequency of any cylinder is twice the frequency of revolution ofthe engine. The frequency of revolution of the engine may be describedas the first engine order. Such a first order frequency component canshow up in the frequency content of the measured generator parameter.The firing frequency of a given cylinder of a four stroke engine may bedescribed as the half engine order, where the half engine order is onehalf the frequency of revolution of the engine. Such a half orderfrequency component can also show up in the frequency content of themeasured dc-link parameter. Similarly, various auxiliary systems (fans,pumps, compressors, traction motors, etc.) may have cyclical componentsthat also can produce frequency components that appear in the dc-linkparameter.

As another example of a four stroke engine, a twelve cylinder engine mayhave a firing sequence of 1-7-5-11-3-9-6-12-2-8-4-10, where eachcylinder fires once for every two revolutions of the engine. Thus, thefiring frequency of a given cylinder is one half the frequency ofrevolution of the engine and the firing frequency of any cylinder is sixtimes the frequency of revolution of the engine. As an example of a twostroke engine, a twelve cylinder engine may have a firing sequence of1-7-5-11-3-9-6-12-2-8-4-10, where each cylinder fires once for everyrevolution of the engine. Thus, the firing frequency of a given cylinderis the frequency of revolution of the engine and the firing frequency ofany cylinder is twelve times the frequency of revolution of the engine.Again, these frequency components can show up in the frequency contentof the measured dc-link parameter.

For example, the engine may be a four stroke engine operating at 1050RPM. Thus, the first engine order is at 17.5 Hz and the half engineorder is at 8.75 Hz. The dc-link voltage may vary with a periodicfrequency as the engine shaft 111 rotates during operation. For example,the frequency content of the dc-link voltage may include a frequencycomponent at the frequency of the first engine order. In other words,the peak magnitude of the frequency content may occur at the first-orderfrequency component. The dc-link voltage may also include frequencycontent at other harmonics of the first-order frequency, such as at asecond-order frequency (twice the engine frequency), a third-orderfrequency (three times the engine frequency), etc. Similarly, thedc-link voltage may include frequency content at frequencies less thanthe first-order frequency, such as at a half-order frequency (half theengine frequency).

For an engine or auxiliary system that is “healthy” and is operatingproperly, the frequency content of the measured dc-link parameter canhave a particular healthy signature. Deviations from such a healthysignature can indicate a problem with the engine or auxiliary system.For example, in accordance with an embodiment, a condition of anauxiliary system may be diagnosed by analyzing a half order magnitudeand/or phase of the frequency content.

FIG. 4 is an illustration showing example embodiments of “healthy” and“unhealthy” frequency content. The frequency content 410 of the healthyauxiliary system (i.e., an auxiliary system that is operating properly)has three frequency components of absolute and relative magnitudes asshown in FIG. 4, in accordance with an embodiment. The frequency content420 of the unhealthy engine (i.e., an auxiliary system that is notoperating properly due to some degradation or failure) has threefrequency components at the same locations as in the frequency content410 for the healthy engine. However, the amplitude of one frequencycomponent 421 (e.g., a half order component) is distorted (e.g.,increased in amplitude), and the amplitude of another frequencycomponent 423 (e.g., a second order component) is also distorted (e.g.,decreased in amplitude), in accordance with an embodiment. The distortedfrequency components 421 and 423 in the frequency content 420 areindicative of an unhealthy auxiliary system. Furthermore, the particularcharacteristics of the distorted frequency components (e.g., amplitude)relative to the other frequency components in the frequency content 420of the unhealthy auxiliary system can be indicative of a particular typeof degradation or failure. Also, the phase of the half order component,with respect to a reference component of the auxiliary system, may beused to isolate a problem to a particular component of the auxiliarysystem.

The degraded components may cause the auxiliary system to operate lessefficiently. Further, the condition of the degraded components mayaccelerate degradation of the components which may increase thelikelihood of catastrophic auxiliary system failure and road failure.The diagnosis may include both a warning of degradation as well as anindication of the type and/or location of the degraded auxiliary systemcomponent.

FIG. 5 is an illustration of an embodiment of how a diagnostic logic 510in the controller 150 can detect an unhealthy condition in the frequencycontent of a dc-link parameter. For example, the half order component421 can be compared to a threshold level T by the diagnostic logic 510.If the magnitude of the component 421 exceeds the threshold level T,then the diagnostic logic 510 determines that degradation in anauxiliary system has occurred. Furthermore, if the diagnostic logic 510determines that the ratio of the half order component to the first ordercomponent 422 exceeds a second threshold level, and the ratio of thefirst order component to the second order component 423 exceeds a thirdthreshold level, then the diagnostic logic 510 isolates the degradationto a particular auxiliary system component. In accordance with anembodiment, the diagnostic logic includes computer executableinstructions that are executed by the processor 152. In accordance withan embodiment, the ratio of a half order component to a dc or zero ordercomponent can be indicative of an auxiliary equipment problem.Furthermore, the threshold level T can be dependent on an operatingcondition of the auxiliary equipment such as, for example, power, speed,ambient conditions, repair history, etc.

Types of auxiliary system degradation or failures that can be diagnosed,distinguished, and isolated may include an unbalanced radiator fan, afaulty compressor, and a degraded traction motor, for example. Once adegradation or failure is diagnosed, an action can be taken. Suchactions may include, for example, providing a warning signal to theoperator (e.g., via the display 180), adjusting an auxiliary systemoperating parameter (e.g., derating the auxiliary system power, shuttingdown a portion of the auxiliary system, shutting down the auxiliarysystem entirely), logging a maintenance action, and transmitting thediagnosed condition to a central location (e.g., via the communicationssystem 190).

FIG. 6 is an illustration of an example embodiment of how to isolate adegradation to a particular auxiliary system. A particular frequencycomponent of the frequency content out of the FFT process or thebandpass filtering process is tracked (in frequency) by a phase-lockedloop (PLL) process 610 of the controller 150. A frequency component canmove around due to a change in an operating condition (e.g., compressorspeed, radiator fan speed, engine speed, etc.) In accordance with anembodiment, the operating condition, state, or mode (e.g., speed) of aparticular auxiliary system (e.g., the radiator fan 143) can be variedby the controller 150. If the particular frequency component varies (astracked by the PLL process) in correspondence with the varying operatingcondition, state, or mode of the particular auxiliary system, then thatparticular frequency component is correlated to that particularauxiliary system. The amplitude and/or phase of the tracked frequencycomponent out of the PLL process can be compared to one or morethresholds to diagnose the particular problem (e.g., particular degradedcomponent) within the isolated auxiliary system.

In accordance with an embodiment, a plurality of frequency components ofthe frequency content of the dc-link voltage (or dc-link current) aretracked continuously and correlated to particular auxiliary equipment.If a particular frequency component does not correlate to a particularauxiliary system, then a condition, state, or operating condition of theengine 110 (e.g., speed) can be varied to determine if the particularfrequency component correlates to the engine. In this manner,distinctions can be made between engine degradation and auxiliaryequipment degradation. In accordance with an embodiment, the variousauxiliary systems provide feedback to the controller 150 (via sensorindicators) such that the controller is aware of which condition ofwhich auxiliary system is varying.

As a result, if a particular frequency component suddenly appears in thefrequency content of the dc-link voltage, the techniques describedherein can be employed to isolate the frequency component to the engineor to auxiliary equipment. If the engine is ruled out, then thetechniques described herein can further be employed to isolate to aparticular auxiliary system, and ultimately to a particular problem witha particular auxiliary system. For example, a 12 Hz frequency componentthat suddenly appears in the frequency content of the dc-link voltage isruled out as corresponding to the engine by varying the engine speed.Operating states of the radiator fan 143, the compressor 142, the blower141, and the traction motor 130 are successively varied by thecontroller 150 until, finally, the 12 Hz component is isolated to thetraction motor 130. The amplitude of the 12 Hz component is thencompared to several thresholds and it is determined that a catastrophicfailure of the traction motor 130 is likely to occur soon. As a result,the traction motor 130 is shut down.

Referring again to FIG. 2, various mechanically driven auxiliaryequipment 144 can be operatively coupled to the rotating shaft 111 ofthe engine 110. Examples of such mechanically driven equipment mayinclude pumps and engine cooling systems. In accordance with anembodiment, the rotating shaft speed of the engine 110 is measured(e.g., via the speed sensor 160) and the controller 150 diagnoses acondition of the auxiliary equipment based on frequency content of theshaft speed.

Again, a Fourier transform process 310 or a bandpass filtering process320 can be used to determine the frequency content of the shaft speed.For auxiliary systems that operate intermittently, time-frequencyanalysis techniques such as short time Fourier transform or wavelettransform may be used. The controller 150 is configured to analyze oneor more components of the frequency content, isolate to a particularauxiliary system coupled to the rotating shaft 111, and diagnose thecondition of the particular auxiliary system. In accordance with anembodiment, the engine 110, or any of the auxiliary equipment, may firstbe driven to a specified operating condition, state, or mode beforediagnosing the auxiliary equipment. For example, if a frequencygenerated by the engine is the same as or very close to a frequencyproduced by the auxiliary equipment during the diagnosis, then themode/frequency of operation of the engine, auxiliary equipment, or bothcan be changed to provide a frequency separation. This separation can beperformed during the time of diagnosis.

Again, FIG. 6 is an illustration of an example embodiment of how toisolate a degradation to a particular auxiliary system. A particularfrequency component of the frequency content out of the FFT process orthe bandpass filtering process is tracked (in frequency) by aphase-locked loop (PLL) process 610 of the controller 150. In accordancewith an embodiment, the operating condition, state, or mode (e.g.,pressure) of a particular auxiliary system (e.g., a pump) can be variedby the controller 150. If the particular frequency component varies (astracked by the PLL process) in correspondence with the varying operatingcondition, state, or mode of the particular auxiliary system, then thatparticular frequency component is correlated to that particularauxiliary system. The amplitude and/or phase of the tracked frequencycomponent can be compared to one or more thresholds to diagnose theparticular problem with the isolated auxiliary system.

In accordance with an embodiment, a plurality of frequency components ofthe frequency content of the shaft speed are continuously tracked andcorrelated to particular auxiliary equipment coupled to the shaft 111.In accordance with an embodiment, the various auxiliary systems providefeedback to the controller 150 such that the controller is aware ofwhich condition of which auxiliary system is varying. As a result, if aparticular frequency component suddenly appears in the frequency contentof the speed signal, the techniques described herein can be employed toisolate the frequency component to the auxiliary equipment and,ultimately, to a particular problem with a particular auxiliary system.

In accordance with an embodiment, the controller 150 is operable toreport a degraded auxiliary equipment condition, for example, via thedisplay 180 and the communication system 190. Furthermore, in accordancewith an embodiment, the controller 150 includes instructions configuredto adjust an auxiliary equipment operating parameter (e.g., fan speed)based on the diagnosed condition.

An embodiment includes a test kit having a controller that is operableto determine a condition of auxiliary equipment electrically coupled toa generator based on frequency content of a measured dc-link parameterassociated with the generator over time. The test kit may furtherinclude a sensor to sense the dc-link parameter (e.g., voltage orcurrent) associated with the generator. The controller is furtheroperable to communicate with the sensor to sample the dc-link parameterover time and to extract the frequency content of the dc-link parameter.

Another embodiment includes a test kit having a controller that isoperable to determine a condition of auxiliary equipment operativelycoupled to a rotating shaft of a reciprocating engine based on frequencycontent of a measured speed of the shaft over time. The test kit mayfurther include a sensor to sense the speed of the shaft. The controlleris further operable to communicate with the speed sensor to sample thespeed over time and to extract frequency content of the speed.

As an alternative, instead of employing a PLL process, the dc-linkvoltage (or dc-link current) or the speed signal can be processed by abank of bandpass filters in the controller 150, each tuned to aparticular frequency corresponding to operation under particularconditions. Root-mean-square (RMS) values of the filtered signals (orsome other combination, e.g., average, of the filtered signals) providean indication of the health of the auxiliary components (e.g., bycomparing the RMS values to determined threshold values). FIG. 7 is anillustration of an example embodiment of how to diagnose a condition ofauxiliary equipment using a bank of tuned bandpass filters 710 alongwith a RMS process 720 and a comparator process 730 provided by thecontroller (e.g., in the form of computer executable instructions, forexample).

Again, instead of employing a PLL process, the dc-link voltage or thespeed signal can be processed by the FFT process or the bandpassfiltering process and patterns in the frequency content can be analyzedby the controller to determine failure modes or degradation of theauxiliary equipment. Various harmonics in the frequency content can becorrelated to particular auxiliary equipment by knowing in advance thefundamental frequency of operation of the particular auxiliary systems.For example, a 12 Hz sub-harmonic frequency may be correlated to anauxiliary system operating at a fundamental frequency of 24 Hz.

Both the frequency content of the speed signal and the frequency contentof the dc-link voltage (or dc-link current) can be used to diagnose acondition of the auxiliary equipment. The various techniques describedherein may be combined in particular ways, using both speed and dc-linksignals, to distinguish from the engine, isolate to a particularauxiliary system, and further isolate to a particular component of theauxiliary system.

Further examples of applications of systems and methods described hereinare now provided. The examples illustrate various approaches fordiagnosing and distinguishing between different types of auxiliarysystem degradation based on the frequency content of dc-link data and/orengine speed data.

In one embodiment, a degraded auxiliary system may be detected based ona frequency content signature, such as the magnitude of the half-orderfrequency component being greater than a half-order threshold value. Inan alternate embodiment, the magnitudes of the frequency content may beintegrated over the range of frequencies, and a degraded component of anauxiliary system may be detected based on the integration being greaterthan an integral threshold value.

Detection of one degraded component, where the other components of theauxiliary system are more healthy (or less degraded), may have a moreclear frequency content signature than when multiple components of theauxiliary system are degraded. For example, the frequency contentsignature of one degraded component may be identified by comparing themagnitude of the half-order frequency component to a half-ordermagnitude threshold value. However, multiple degraded components mayhave a different frequency component signature than a single degradedcomponent. Further, the position in the operating sequence order ofmultiple degraded components may change the frequency content signature.For example, two degraded components 180° out of phase may have adifferent frequency component signature than two degraded components insuccessive operating sequence order, and thus the methods disclosedherein may identify one or more degraded components based on variouschanges in the frequency content signature. Further, it may bebeneficial to generate a frequency content signature of a healthyauxiliary system by recording frequency content at various frequenciesand operating conditions. In one embodiment, the frequency content of anauxiliary system may be compared to the frequency content signature of ahealthy auxiliary system. Anomalies not matching the frequency contentsignature of the healthy auxiliary system or a different degradedauxiliary system component may be identified and reported by thecontroller, for example.

In one embodiment, the time-domain dc-link data may be filtered by alow-pass filter with a cut-off frequency slightly greater than thefirst-order frequency. For example, the cut-off frequency may be ten totwenty percent greater than the first-order frequency. Thus, in oneembodiment, the cut-off frequency may be determined by the engine speed.The dc-link data may be sampled in time at a frequency greater than orequal to the Nyquist rate. In one embodiment, the time-domain signal maybe sampled at a frequency greater than twice the first engine orderfrequency (or first auxiliary system order frequency). In oneembodiment, the time-domain signal may be sampled at a frequency greaterthan twice the engine red-line frequency. Thus, by low-pass filteringand sampling at a frequency greater than or equal to the Nyquist rate,the frequency content of the dc-link data may not be aliased. The samemay applied for speed data of the engine.

As discussed herein, the sampled dc-link data (e.g., dc-link voltage,dc-link current) and/or engine speed data may be transformed to generatea frequency domain frequency content. In one embodiment, a fast Fouriertransform may be used to generate the frequency domain frequencycontent. In one embodiment, a correlation algorithm may be applied tocompare the frequency content of the dc-link data and/or engine speeddata, to a signature for a condition of an auxiliary system. Forexample, the signature for a healthy auxiliary system may includefrequency content at the first-order frequency with a magnitude below afirst-order threshold value and frequency content at the half-orderfrequency with a magnitude below a half-order threshold value. Thefirst-order threshold value may correspond to an operational state ofthe auxiliary system.

For example, the historical auxiliary system data may be stored in adatabase including samples of frequency content from earlier operationof the auxiliary system. Thus, a trend in frequency content may bedetected and the trend may be used to determine the health of theauxiliary system. For example, an increasing magnitude at the half ordercomponent for a given radiator fan speed and load may indicate that aradiator fan is degrading.

In one embodiment, frequency content of the dc-link data and/or enginespeed data may be stored in a database including historical auxiliaryequipment data. For example, the database may be stored in memory 154 ofcontroller 150. As another example, the database may be stored at a siteremote from rail vehicle 106. For example, historical data may beencapsulated in a message and transmitted with communications system190. In this manner, a command center may monitor the health of theauxiliary equipment in real-time. For example, the command center mayperform steps to diagnose the condition of the auxiliary equipment usingthe dc-link data and/or engine speed data transmitted withcommunications system 190. For example, the command center may receivedc-link voltage data from rail vehicle 106, frequency transform thedc-link voltage data, apply a correlation algorithm to the transformeddata, and diagnose potential degradation of an auxiliary system.Further, the command center may schedule maintenance and deploy healthylocomotives and maintenance crews in a manner to optimize capitalinvestment. Historical data may be further used to evaluate the healthof the auxiliary equipment before and after equipment service, equipmentmodifications, and equipment component change-outs.

In one embodiment, a potential fault may be reported to the locomotiveoperating crew via display 180. Once notified, the operator may adjustoperation of rail vehicle 106 to reduce the potential of furtherdegradation of the auxiliary equipment. In one embodiment, a messageindicating a potential fault may be transmitted with communicationssystem 190 to a command center. Further, the severity of the potentialfault may be reported. For example, diagnosing a fault based onfrequency content of dc-link data and/or engine speed data may allow afault to be detected earlier than when the fault is diagnosed with onlyaverage auxiliary system information. Thus, the auxiliary system maycontinue to operate when a potential fault is diagnosed in the earlystages of degradation. In contrast, it may be desirable to stop theauxiliary system or schedule prompt maintenance if a potential fault isdiagnosed as severe. In one embodiment, the severity of a potentialfault may be determined according to a difference between a thresholdvalue and the magnitude of one or more components of the frequencycontent of the dc-link and/or speed data.

By analyzing the frequency content of dc-link data and/or engine speeddata, it may be possible to monitor and diagnose the auxiliary equipmentduring operation. Further, operation of an auxiliary system with adegraded component may be adjusted to potentially reduce additionaldegradation of the component and to potentially reduce the likelihood ofadditional auxiliary system failure and in-use failure. For example, thehalf-order component may be compared to a half-order threshold value. Inone embodiment, if the magnitude of the half-order component is greaterthan the half-order threshold value, the potential fault may be adegraded a first degraded component. However, if the magnitude of thehalf-order component is not greater than the half-order threshold value,the potential fault may be a second degraded component.

In one embodiment, the potential fault may be reported to the locomotiveoperating crew via display 180 and the operator may adjust operation ofrail vehicle 106 to reduce the potential of further degradation. In oneembodiment, a message diagnosing the potential fault may be transmittedwith communications system 190 to a command center.

In one example, the half-order frequency component of the dc-link and/orspeed data may be monitored for each disabled component of an auxiliarysystem. The component may be degraded when the half-order frequencycomponent drops below a half-order threshold value while the componentis disabled. The component may be a healthy component when thehalf-order frequency component remains above the half-order thresholdvalue while the component is disabled. In other words, the degradedcomponent may be the component that contributes a higher amount offrequency content at the half-order frequency component than otherauxiliary system components. In one embodiment, the selective disablingdiagnosis may be performed when the auxiliary system is operating atidle or lightly loaded.

It may be more desirable to switch off an auxiliary system than to havea degraded component fail in a manner that may cause additional damageto the auxiliary system. In one embodiment, a threshold value may bedetermined that indicates continued operation of the auxiliary systemmay be undesirable because the potential fault is severe. For example,the potential fault may be judged as severe if a magnitude of thehalf-order frequency component exceeds a threshold value. The auxiliarysystem may be stopped if the severity of the potential fault exceeds thethreshold value.

A request to schedule service may be sent, such as by a message sent viacommunications system 190, for example. Further, by sending thepotential fault condition and the severity of the potential fault,down-time of rail vehicle 106 may be reduced. For example, service maybe deferred on rail vehicle 106 when the potential fault is of lowseverity. Down-time may be further reduced by derating power of theauxiliary system, such as by adjusting an auxiliary system operatingparameter based on the diagnosed condition. It may be determined ifderating of the auxiliary system is enabled. For example, derating thepower of the auxiliary system may reduce the magnitude of one or morecomponents of the frequency content of the dc-link data.

In one embodiment, a test kit may be used for identifying frequencycontent of the dc-link data and/or engine speed data and diagnosing acondition of the auxiliary equipment based on the frequency content ofthe data. For example, a test kit may include a controller that isoperable to communicate with one or more dc-link sensors and/or enginespeed sensors and operable to sample the associated data. The controllermay be further operable to transform signals from the one or moresensors into a frequency content that represents frequency informationof the auxiliary equipment. The controller may be further operable todiagnose a condition of the auxiliary equipment based on the frequencycontent of the generator data from the sensors. The test kit may furtherinclude one or more sensors for sensing dc-link parameters (e.g.,dc-link voltage) and/or engine parameters (e.g., engine speed).

In the specification and claims, reference will be made to a number ofterms have the following meanings. The singular forms “a”, “an” and“the” include plural referents unless the context clearly dictatesotherwise. Approximating language, as used herein throughout thespecification and claims, may be applied to modify any quantitativerepresentation that could permissibly vary without resulting in a changein the basic function to which it is related. Accordingly, a valuemodified by a term such as “about” is not to be limited to the precisevalue specified. In some instances, the approximating language maycorrespond to the precision of an instrument for measuring the value.Similarly, “free” may be used in combination with a term, and mayinclude an insubstantial number, or trace amounts, while still beingconsidered free of the modified term. Moreover, unless specificallystated otherwise, any use of the terms “first,” “second,” etc., do notdenote any order or importance, but rather the terms “first,” “second,”etc., are used to distinguish one element from another.

As used herein, the terms “may” and “may be” indicate a possibility ofan occurrence within a set of circumstances; a possession of a specifiedproperty, characteristic or function; and/or qualify another verb byexpressing one or more of an ability, capability, or possibilityassociated with the qualified verb. Accordingly, usage of “may” and “maybe” indicates that a modified term is apparently appropriate, capable,or suitable for an indicated capacity, function, or usage, while takinginto account that in some circumstances the modified term may sometimesnot be appropriate, capable, or suitable. For example, in somecircumstances an event or capacity can be expected, while in othercircumstances the event or capacity cannot occur—this distinction iscaptured by the terms “may” and “may be”. The terms “generator” and“alternator” are used interchangeably herein (however, it is recognizedthat one term or the other may be more appropriate depending on theapplication). The terms “frequency content” and “harmonic content” areused interchangeably herein and can refer to fundamental frequency(and/or phase) components and associated harmonic frequency (and/orphase) components above and below the fundamental components. The term“instructions” as used herein with respect to a controller or processormay refer to computer executable instructions.

The embodiments described herein are examples of articles, systems, andmethods having elements corresponding to the elements of the inventionrecited in the claims. This written description may enable those ofordinary skill in the art to make and use embodiments having alternativeelements that likewise correspond to the elements of the inventionrecited in the claims. The scope of the invention thus includesarticles, systems and methods that do not differ from the literallanguage of the claims, and further includes other articles, systems andmethods with insubstantial differences from the literal language of theclaims. While only certain features and embodiments have beenillustrated and described herein, many modifications and changes mayoccur to one of ordinary skill in the relevant art. The appended claimscover all such modifications and changes.

What is claimed is:
 1. A method for auxiliary equipment electricallycoupled to a generator that is operationally connected to areciprocating engine, comprising: measuring a dc-link parameterassociated with the generator during operation using a dc-link sensor;and diagnosing a condition of the auxiliary equipment based on frequencycontent of the dc-link parameter using at least a processor.
 2. Themethod of claim 1, wherein the dc-link parameter is a dc-link voltage.3. The method of claim 1, wherein the dc-link parameter is a dc-linkcurrent.
 4. The method of claim 1, wherein the reciprocating engine isfirst driven to a specified operating condition, state, or mode.
 5. Themethod of claim 1, wherein the frequency content of the dc-linkparameter is determined by performing a Fourier transform process on thetime domain dc-link parameter.
 6. The method of claim 1, wherein thefrequency content of the dc-link parameter is determined by performing aband-pass filtering process on the time domain dc-link parameter.
 7. Themethod of claim 1, further comprising tracking at least one component ofthe frequency content as an operating condition, state, or mode of atleast one of the reciprocating engine and the auxiliary equipment isvaried.
 8. The method of claim 7, wherein the tracking of the frequencycomponent is accomplished using a phase-locked loop.
 9. The method ofclaim 7, wherein the tracking of the frequency component is accomplishedusing a set of band-pass filters.
 10. The method of claim 7, furthercomprising correlating the tracked frequency component to one of thevaried reciprocating engine and the varied auxiliary equipment.
 11. Amethod for auxiliary equipment operationally coupled to a rotating shaftof a reciprocating engine, comprising: measuring a rotating shaft speedof the reciprocating engine during operation using a speed sensor; anddiagnosing a condition of the auxiliary equipment based on frequencycontent of the shaft speed using at least a processor.
 12. The method ofclaim 11, wherein the reciprocating engine is first driven to aspecified operating condition, state, or mode.
 13. The method of claim11, wherein the frequency content of the shaft speed is determined byperforming a Fourier transform process on the time domain shaft speed.14. The method of claim 11, wherein the frequency content of the shaftspeed is determined by performing a band-pass filtering process on thetime domain dc shaft speed.
 15. The method of claim 11, furthercomprising tracking at least one component of the frequency content asan operating condition, state, or mode of at least one of thereciprocating engine and the auxiliary equipment is varied.
 16. Themethod of claim 15, wherein the tracking of the frequency component isaccomplished using a phase-locked loop.
 17. The method of claim 15,wherein the tracking of the frequency component is accomplished using aset of band-pass filters.
 18. The method of claim 15, further comprisingcorrelating the tracked frequency component to one of the variedreciprocating engine and the varied auxiliary equipment.
 19. A vehiclesystem, comprising: a generator; auxiliary equipment electricallycoupled to the generator; a dc-link sensor for measuring a dc-linkparameter associated with the generator during operation; and acontroller including instructions configured to: sample and transformthe measured dc-link parameter; identify frequency content of thedc-link parameter; and diagnose a condition of the auxiliary equipmentbased on the frequency content of the dc-link parameter.
 20. The vehiclesystem of claim 19, wherein the dc-link parameter is a dc-link voltage.21. The vehicle system of claim 19, wherein the dc-link parameter is adc-link current.
 22. The vehicle system of claim 19, wherein thecontroller is operable to report a degraded auxiliary equipmentcondition.
 23. The vehicle system of claim 19, wherein the controllerfurther includes instructions configured to adjust an auxiliaryequipment operating parameter based on the diagnosed condition.
 24. Avehicle system, comprising: a reciprocating engine having a rotatingshaft; auxiliary equipment operatively coupled to the rotating shaft; asensor for measuring a speed of the rotating shaft over time duringoperation; and a controller including instructions configured to: sampleand transform the measured speed; identify frequency content of thespeed; and diagnose a condition of the auxiliary equipment based on thefrequency content of the speed.
 25. The vehicle system of claim 24,wherein the controller is operable to report a degraded auxiliaryequipment condition.
 26. The vehicle system of claim 24, wherein thecontroller further includes instructions configured to adjust anauxiliary equipment operating parameter based on the diagnosedcondition.